The invention relates to a device for the inspection of welds between a tubular stub and a wall, comprising a rotatably driven central shaft with a test probe, such as an ultrasonic probe, which probe can be rotated and can be moved in the axial direction of the stub.
Such a device is very well known in practice. With this the probe is gradually or continuously moved axially in respect of the stub and is rotated simultaneously.
During each revolution a given level of the weld joint is scanned so that it can be determined whether cracks or such like are present in it. In this way the weld joint is scanned over its entire height.
This does not give difficulties when the angle between the tubular stub and the wall is 90.degree..
In particular in case of nuclear reactor vessels, however, but also in case of steam boilers often a hemispherical or in any case an arcuate bottom and head is used, with which the tubular stubs are running parallel to each other.
This means that each tubular stub not being positioned at the same radius is positioned at an other angle to the wall. Only a centrally positioned tubular stub is situated at a right angle to the tangential plane of the top of the wall.
When, with the known device, the weld joint of a tubular stub that has to be scanned is positioned at an oblique angle, then only a part of the circumference of the weld joint is scanned at each level. So the record of the scanning has no closed formation (i.e., the probe does not follow the oblique weld along its entire path). It is thus difficult to locate the position of material defects, if any.
Further the known test probe has to be gradually or continuously moved over a great height, to wit from the heighest point of the weld joint to the opposite lying lowest point. By virtue of this, the inspection takes a rather long time. During one revolution, the angle between the centerline of the probe and the wall of the tubular stub remains the same. In case of an obliquely positioned weld joint this means that the angle between the centerline of the probe and the weld joint varies continuously. Consequently, a good inspection of the weld joint is obstructed too, because the geometry of the weld is changing continuously.